What is the chemical reaction occurs in iodine to stain the cell?

Iodine interacts with CV+(crystal violet dissociates into CV+ in aqueous solution) and forms large complexes of crystal violet and iodine (CV–I) within the inner and outer layers of the cell. Iodine is often referred to as a mordant, but is a trapping agent that prevents the removal of the CV-I complex and, therefore, color the cell.